FIG. 1 presents an aeronautical communication system for communicating between aircraft 11.1, 11.2, 11.3, 11.4 and a ground unit 12. The system uses a satellite communication resource, called return channel resource, enabling messages to be transmitted from the aircraft 11.1, 11.2, 11.3, 11.4 to the ground unit 12. Each of the aircraft 11.1, 11.2, 11.3, 11.4 includes embedded applications and a terminal for communicating with the ground unit. The messages sent by the aircraft are associated with services. Among those that can be cited, there are, for example: the COTRAC (Common Trajectory Coordination) service which enables the pilot and the air traffic controller to coordinate the trajectory of the aircraft in real time. A message of a service which has a certain size is associated with a priority and a communication network end-to-end delay requirement.
The network formed by the aircraft and the ground unit is managed by a Network Control Center (NCC) 13 responsible for sharing the satellite communication resource between the aircraft (the number of which may be greater than several thousand).
The ground unit transmits the messages to a terrestrial network 15 linking Airline Operation Control (AOC) centers 16.1 and air traffic controllers 17.1, connected to the air traffic management network via Air Navigation Service Providers (ANSP) 17.2.
The traffic profiles used in the aeronautical communications for the air traffic management have very specific characteristics. The first characteristic is that the messages transmitted by the aircraft are very sporadic. The frequency of transmissions of messages by the aircraft is in fact very low. The second characteristic is that there are very strict time constraints to be observed for the messages of a service. For example, the routing delay from end to end in the network must be observed by 95% of the messages.
The control centers according to the prior art do not take these time constraints into account. This is because, even with fairly low traffic loads involving few aircraft, temporary traffic peaks may occur. This can therefore lead to a failure to observe the time constraints, particularly for the longest messages.
Centralized allocation methods are known which allow multiple access to a resource in a telecommunication context, taking into account the constraints of the services. These methods rely on an assumption of a more or less sustained traffic flow and cannot, for the most part, be applied to the context of aeronautical communications. By using the methods applicable to communications for air traffic management, it is found that, even with an average communication bit rate well below the capacity of the resource, some services fail to observe their time requirements.
So-called random allocation methods are also known which allow multiple access to a resource and do not require any prior reservation or centralized management of the resource. The advantage of this type of access is that it is easy to implement and allows immediate access to the resource, in the case where there is no collision between the message fragments transmitted by different terminals. Otherwise, retransmissions of these fragments are necessary. It will therefore be understood that this type of access does not make it possible to guarantee strong time requirements, particularly for long messages for which the probability of collision of one of the fragments is high.